1. Field of the Invention
The present invention relates to a monolithic refractory material, and particularly to a monolithic refractory material having a low moisture content, excellent casting workability, and both corrosion resistance and spalling resistance. Particularly, this material is suitable as a casting monolithic refractory material for lining a torpedo ladle car.
2. Description of the Related Art
In a steel making process, a torpedo ladle car is used as a transport container for transporting a hot metal from the blast furnace to the converter, and a pre-processing bath for removing impurities such as silicon, sulfur, phosphorus, and the like, from the hot metal.
Although lining of the torpedo ladle car is generally carried out by brick laying, casting of a monolithic refractory as a lining has recently been investigated.
A material for lining the torpedo ladle car is required to have corrosion resistance which allows the material to resist the severely corrosive slag by-produced from the flux used in the above-described pre-processing of a hot metal, and resistance to spalling (referred to as "spalling resistance" hereinafter) in a working environment in which the outer periphery is confined by a shell.
From this viewpoint, an alumina-SiC-graphite brick provides excellent corrosion resistance due to the prevention of wetting with a slag, which is caused by the effect of the SiC and graphite contained therein, and maintains the high spalling resistance due to low thermal expansion, low elastic modulus, and high heat conductivity, thereby exhibiting excellent practicability.
However, in an attempt to produce a casting material by adding equal amounts of SiC and graphite of the same type as brick, a large amount of water is required for ensuring casting workability because of the low water wettability of graphite, and thus the final resultant product has an extremely high porosity, and very low practicability.
Namely, for a monolithic refractory material, it is necessary to ensure sufficient workability by adding a small amount of water, and to ensure durability close to the durability of brick. It is difficult to satisfy both of these requirements.
In order to solve the above problem, a method (refer to Japanese Unexamined Patent Publication No. 6-166574) has been previously proposed, in which an oxide such as alumina or the like, which has excellent water wettability, is ground and adhered to graphite. However, the raw material cost of the monolithic refractory is increased due to the processing cost, thereby limiting practical use of this method.
Another known method comprises applying a mechanical impact to artificial graphite or crystalline graphite (refer to Japanese Unexamined Patent Publication Nos. 8-183666 and 301667). This method also has the same economic problem as the above-described conventional technique.
Other methods are also known, in which anthracite (refer to Japanese Unexamined Patent Publication No. 8-83667) or amorphous graphite is used. It is difficult, however, to obtain an effect on the corrosion resistance and the spalling resistance by adding such materials to brick in the same manner as crystalline graphite.
As described above, at present, there is no economical casting refractory material for lining torpedo ladle cars having a low moisture content and excellent casting workability, and both corrosion resistance and spalling resistance.